Help selecting interface for optane

I can use the included m2 to u2 adapter and connect the optane to the first NVME slot which goes to the cpu or I can use this card

and put the optane in the third vacant pcie slot (which runs at pcie 3,4, or 5 depending on the mother board)

Since the 4800x has pcie3, bandwidthe from the motherboard should be no factor. But does the added latency of the third slot going through a chipset add latency? Any hard numbers wendell? I think there are a few motherboards where the third pcie slot goes to the cpu (but they are expensive and also unnecessarily pcie gen5)

I have an ASUS ROG X670E Crosshair Extreme. PCIe 5.0 connectivity throughout. I tested the difference between the PCIe 5.0 slots (connected to the CPU) and the PCIe 4.0 slots going through the chipset. I got an 8% drop in random 4K read performance.

4K random read test with 3 Optane SSDs and one Samsung SSD